US8107155B2 - System and method for reducing visual artifacts in displays - Google Patents

Abstract

Embodiments include systems and methods for reducing visible artifacts such as Moiré, or interference, patterns, in displays. One embodiment includes a display device comprising a plurality of light modulators and a plurality of illumination elements configured to direct light to the light modulators. The directed light of the plurality of illumination elements collectively defines an nonuniformly varying pattern of light.

Description

BACKGROUND OF THE INVENTION

1. Field

The field of the invention relates to display systems.

2. Description of the Related Technology

Display systems may include light modulators to produce a displayed image by modulating light directed to the light modulators. Such display systems may include a source of illumination to at least partly provide light to the light modulators. One embodiment of a light modulator comprises microelectromechanical systems (MEMS). Micromechanical elements may be created using deposition, etching, and or other micromachining processes that etch away parts of substrates and/or deposited material layers or that add layers to form electrical and electromechanical devices. One type of MEMS device is called an interferometric modulator. As used herein, the term interferometric modulator or interferometric light modulator refers to a device that selectively absorbs and/or reflects light using the principles of optical interference. In certain embodiments, an interferometric modulator may comprise a pair of conductive plates, one or both of which may be transparent and/or reflective in whole or part and capable of relative motion upon application of an appropriate electrical signal. In a particular embodiment, one plate may comprise a stationary layer deposited on a substrate and the other plate may comprise a metallic membrane separated from the stationary layer by an air gap. As described herein in more detail, the position of one plate in relation to another can change the optical interference of light incident on the interferometric modulator. Such devices have a wide range of applications, and it would be beneficial in the art to utilize and/or modify the characteristics of these types of devices so that their features can be exploited in improving existing products and creating new products that have not yet been developed. For example, a need exists for improved illumination sources for light modulator based displays.

SUMMARY OF CERTAIN INVENTIVE ASPECTS

The system, method, and devices of the invention each have several aspects, no single one of which is solely responsible for its desirable attributes. Without limiting the scope of this invention as expressed by the claims which follow, its more prominent features will now be discussed briefly. After considering this discussion, and particularly after reading the section entitled “Detailed Description” one will understand how the features of this invention provide advantages that include reduced visual artifacts or noise in illuminated display systems.

One embodiment comprises a display device. The display device comprises a plurality of light modulators. The display device further comprises a plurality of illumination elements configured to direct a nonuniformly varying pattern of light to the light modulators.

One embodiment comprises a display device. The display device comprises a plurality of light modulators. The display device further comprises a plurality of illumination elements arranged in a nonuniform pattern and configured to direct light to the light modulators.

One embodiment comprises a display device. The display device comprises a plurality of light modulators. The display device further comprises a plurality of illumination elements configured to direct light to the light modulators. The plurality of illumination elements is adapted to illuminate the light modulators without producing a visible moiré pattern.

One embodiment comprises a display device. The display device comprises means for modulating light. The display device further comprises means for illuminating the light modulating means with a nonuniformly varying pattern of light.

Another embodiment comprises a method of making an illuminator. The method comprises forming a plurality of illumination elements configured to direct a nonuniformly varying pattern of light to an array of light modulators.

Another embodiment comprises a method comprising illuminating a plurality of illumination elements with light. The method further comprises directing a nonuniformly varying pattern of the light from the illumination elements to a plurality of light modulators.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric view depicting a portion of one embodiment of an interferometric modulator display in which a movable reflective layer of a first interferometric modulator is in a relaxed position and a movable reflective layer of a second interferometric modulator is in an actuated position.

FIG. 2 is a system block diagram illustrating one embodiment of an electronic device incorporating a 3×3 interferometric modulator display.

FIG. 3 is a diagram of movable mirror position versus applied voltage for one exemplary embodiment of an interferometric modulator ofFIG. 1.

FIG. 4 is an illustration of a set of row and column voltages that may be used to drive an interferometric modulator display.

FIGS. 5A and 5B illustrate one exemplary timing diagram for row and column signals that may be used to write a frame of display data to the 3×3 interferometric modulator display ofFIG. 2.

FIGS. 6A and 6B are system block diagrams illustrating an embodiment of a visual display device comprising a plurality of interferometric modulators.

FIG. 7A is a cross section of the device ofFIG. 1.

FIG. 7B is a cross section of an alternative embodiment of an interferometric modulator.

FIG. 7C is a cross section of another alternative embodiment of an interferometric modulator.

FIG. 7D is a cross section of yet another alternative embodiment of an interferometric modulator.

FIG. 7E is a cross section of an additional alternative embodiment of an interferometric modulator.

FIG. 8 is a cross section of an example of a display system comprising an array of light modulators, such as devices illustrated inFIG. 1, illuminated by an illuminator.

FIG. 9 is a cross section of an example of display system such as illustrated inFIG. 8 that comprises an array of light modulators illuminated by an illuminator comprising an array of reflective light turning elements.

FIG. 10A is a cross section of an example of an illuminator comprising periodically spaced light turning elements such as illustrated inFIG. 8

FIG. 10B is a perspective view of an example of an illuminator comprising periodically spaced reflective light turning elements such as illustrated inFIG. 10A.

FIG. 10C is a top view of an example of an illuminator comprising periodically spaced reflective light turning elements such as illustrated inFIG. 10B.

FIG. 11A illustrates a cross section view of an illuminator comprising a periodically arranged reflective light turning elements such as illustrated inFIG. 10B.

FIG. 11B illustrates a schematic cross section view of an illuminator comprising a periodically arranged reflective light turning elements and a light modulator array such as illustrated inFIG. 9.

FIG. 12 is a top view exemplifying moiré patterns formed by three sets of two superimposed periodic arrangements of lines.

FIG. 13A illustrates a cross section view of an illuminator comprising nonuniformly arranged reflective light turning elements.

FIG. 13B illustrates a schematic cross section view of an illuminator comprising a nonuniformly arranged reflective light turning elements and a light modulator array such as illustrated inFIG. 13A.

FIG. 14 illustrates a top view of the nonuniformly arranged light turning elements illustrated inFIG. 13A.

FIG. 15A illustrates a top view of another embodiment of an illuminator comprising nonuniformly arranged reflective light turning elements that is conceptually similar to that ofFIG. 13A.

FIG. 15B illustrates a top view of a portion of the array of light turning elements ofFIG. 15A in more detail.

FIG. 16A is a graphical illustration of a uniform distribution illustrative of the distribution of elements in one embodiment of a light turning array such as illustrated inFIG. 15A.

FIG. 16B is a graphical illustration of a normal distribution illustrative of the nonuniform distribution of elements in one embodiment of a light turning array such as illustrated inFIG. 15A

FIG. 17A illustrates a top view of another embodiment of an illuminator comprising nonuniformly arranged reflective light turning elements that is conceptually similar to that ofFIG. 15A.

FIG. 17B illustrates a top view of another embodiment of an illuminator comprising nonuniformly arranged reflective light turning elements that is conceptually similar to that ofFIG. 17A.

FIG. 18A illustrates a cross section view of yet another embodiment of a nonuniformly arranged light turning array that is conceptually similar to that ofFIG. 13A.

FIG. 18B illustrates a schematic cross section view of the nonuniformly arranged light turning array ofFIG. 18A in relation to a display.

DETAILED DESCRIPTION

The following detailed description is directed to certain specific embodiments of the invention. However, the invention can be embodied in a multitude of different ways. In this description, reference is made to the drawings wherein like parts are designated with like numerals throughout. As will be apparent from the following description, the embodiments may be implemented in any device that is configured to display an image, whether in motion (e.g., video) or stationary (e.g., still image), and whether textual or pictorial. More particularly, it is contemplated that the embodiments may be implemented in or associated with a variety of electronic devices such as, but not limited to, mobile telephones, wireless devices, personal data assistants (PDAs), hand-held or portable computers, GPS receivers/navigators, cameras, MP3 players, camcorders, game consoles, wrist watches, clocks, calculators, television monitors, flat panel displays, computer monitors, auto displays (e.g., odometer display, etc.), cockpit controls and/or displays, display of camera views (e.g., display of a rear view camera in a vehicle), electronic photographs, electronic billboards or signs, projectors, architectural structures, packaging, and aesthetic structures (e.g., display of images on a piece of jewelry). MEMS devices of similar structure to those described herein can also be used in non-display applications such as in electronic switching devices.

Light modulator based displays, including reflective and interferometric displays, generally comprise periodically arranged light modulators in order to correspond to pixel layouts of video signals. Such light modulators may be illuminated using an illuminator or light guide that directs a pattern of light to the light modulators. The illuminator may comprise a periodically arranged light turning (and/or light emissive) elements that directs a periodic pattern of light onto the array of light modulators. When the periodically arranged array of light modulators is illuminated with the periodic pattern of light from the illuminator, the superposition of the two periodic arrays may result in visible Moiré patterns. It has been found that nonuniform arrangement of the illumination elements that directs a nonuniformly varying pattern of light onto the light modulators reduces or even substantially eliminates visible Moiré patterns resulting from this superposition in such display systems. Accordingly, several inventive examples of such nonuniformly arranged (e.g., irregularly or aperiodically arranged so as to be uncorrelated with the arrangement of the light modulators) illumination arrays are disclosed herein.

One interferometric modulator display embodiment comprising an interferometric MEMS display element is illustrated inFIG. 1. In these devices, the pixels are in either a bright or dark state. In the bright (“on” or “open”) state, the display element reflects a large portion of incident visible light to a user. When in the dark (“off” or “closed”) state, the display element reflects little incident visible light to the user. Depending on the embodiment, the light reflectance properties of the “on” and “off” states may be reversed. MEMS pixels can be configured to reflect predominantly at selected colors, allowing for a color display in addition to black and white.

FIG. 1 is an isometric view depicting two adjacent pixels in a series of pixels of a visual display, wherein each pixel comprises a MEMS interferometric modulator. In some embodiments, an interferometric modulator display comprises a row/column array of these interferometric modulators. Each interferometric modulator includes a pair of reflective layers positioned at a variable and controllable distance from each other to form a resonant optical cavity with at least one variable dimension. In one embodiment, one of the reflective layers may be moved between two positions. In the first position, referred to herein as the relaxed position, the movable reflective layer is positioned at a relatively large distance from a fixed partially reflective layer. In the second position, referred to herein as the actuated position, the movable reflective layer is positioned more closely adjacent to the partially reflective layer. Incident light that reflects from the two layers interferes constructively or destructively depending on the position of the movable reflective layer, producing either an overall reflective or non-reflective state for each pixel.

The depicted portion of the pixel array inFIG. 1 includes two adjacentinterferometric modulators12aand12b. In theinterferometric modulator12aon the left, a movablereflective layer14ais illustrated in a relaxed position at a predetermined distance from anoptical stack16a, which includes a partially reflective layer. In theinterferometric modulator12bon the right, the movablereflective layer14bis illustrated in an actuated position adjacent to theoptical stack16b.

The optical stacks16aand16b(collectively referred to as optical stack16), as referenced herein, typically comprise of several fused layers, which can include an electrode layer, such as indium tin oxide (ITO), a partially reflective layer, such as chromium, and a transparent dielectric. Theoptical stack16 is thus electrically conductive, partially transparent and partially reflective, and may be fabricated, for example, by depositing one or more of the above layers onto atransparent substrate20. In some embodiments, the layers are patterned into parallel strips, and may form row electrodes in a display device as described further below. The movablereflective layers14a,14bmay be formed as a series of parallel strips of a deposited metal layer or layers (orthogonal to the row electrodes of16a,16b) deposited on top ofposts18 and an intervening sacrificial material deposited between theposts18. When the sacrificial material is etched away, the movablereflective layers14a,14bare separated from theoptical stacks16a,16bby a definedgap19. A highly conductive and reflective material such as aluminum may be used for thereflective layers14, and these strips may form column electrodes in a display device.

With no applied voltage, thecavity19 remains between the movablereflective layer14aandoptical stack16a, with the movablereflective layer14ain a mechanically relaxed state, as illustrated by thepixel12ainFIG. 1. However, when a potential difference is applied to a selected row and column, the capacitor formed at the intersection of the row and column electrodes at the corresponding pixel becomes charged, and electrostatic forces pull the electrodes together. If the voltage is high enough, the movablereflective layer14 is deformed and is forced against theoptical stack16. A dielectric layer (not illustrated in this FIG.) within theoptical stack16 may prevent shorting and control the separation distance betweenlayers14 and16, as illustrated bypixel12bon the right inFIG. 1. The behavior is the same regardless of the polarity of the applied potential difference. In this way, row/column actuation that can control the reflective vs. non-reflective pixel states is analogous in many ways to that used in conventional LCD and other display technologies.

FIGS. 2 through 5 illustrate one exemplary process and system for using an array of interferometric modulators in a display application.

FIG. 2 is a system block diagram illustrating one embodiment of an electronic device that may incorporate aspects of the invention. In the exemplary embodiment, the electronic device includes aprocessor21 which may be any general purpose single- or multi-chip microprocessor such as an ARM, Pentium®, Pentium II®, Pentium III®, Pentium IV®, Pentium® Pro, an 8051, a MIPS®, a Power PC®, an ALPHA®, or any special purpose microprocessor such as a digital signal processor, microcontroller, or a programmable gate array. As is conventional in the art, theprocessor21 may be configured to execute one or more software modules. In addition to executing an operating system, the processor may be configured to execute one or more software applications, including a web browser, a telephone application, an email program, or any other software application.

In one embodiment, theprocessor21 is also configured to communicate with anarray driver22. In one embodiment, thearray driver22 includes arow driver circuit24 and acolumn driver circuit26 that provide signals to a panel or display array (display)30. The cross section of the array illustrated inFIG. 1 is shown by the lines1-1 inFIG. 2. For MEMS interferometric modulators, the row/column actuation protocol may take advantage of a hysteresis property of these devices illustrated inFIG. 3. It may require, for example, a 10 volt potential difference to cause a movable layer to deform from the relaxed state to the actuated state. However, when the voltage is reduced from that value, the movable layer maintains its state as the voltage drops back below 10 volts. In the exemplary embodiment ofFIG. 3, the movable layer does not relax completely until the voltage drops below 2 volts. There is thus a range of voltage, about 3 to 7 V in the example illustrated inFIG. 3, where there exists a window of applied voltage within which the device is stable in either the relaxed or actuated state. This is referred to herein as the “hysteresis window” or “stability window.” For a display array having the hysteresis characteristics ofFIG. 3, the row/column actuation protocol can be designed such that during row strobing, pixels in the strobed row that are to be actuated are exposed to a voltage difference of about 10 volts, and pixels that are to be relaxed are exposed to a voltage difference of close to zero volts. After the strobe, the pixels are exposed to a steady state voltage difference of about 5 volts such that they remain in whatever state the row strobe put them in. After being written, each pixel sees a potential difference within the “stability window” of 3-7 volts in this example. This feature makes the pixel design illustrated inFIG. 1 stable under the same applied voltage conditions in either an actuated or relaxed pre-existing state. Since each pixel of the interferometric modulator, whether in the actuated or relaxed state, is essentially a capacitor formed by the fixed and moving reflective layers, this stable state can be held at a voltage within the hysteresis window with almost no power dissipation. Essentially no current flows into the pixel if the applied potential is fixed.

In typical applications, a display frame may be created by asserting the set of column electrodes in accordance with the desired set of actuated pixels in the first row. A row pulse is then applied to therow1 electrode, actuating the pixels corresponding to the asserted column lines. The asserted set of column electrodes is then changed to correspond to the desired set of actuated pixels in the second row. A pulse is then applied to therow2 electrode, actuating the appropriate pixels inrow2 in accordance with the asserted column electrodes. Therow1 pixels are unaffected by therow2 pulse, and remain in the state they were set to during therow1 pulse. This may be repeated for the entire series of rows in a sequential fashion to produce the frame. Generally, the frames are refreshed and/or updated with new display data by continually repeating this process at some desired number of frames per second. A wide variety of protocols for driving row and column electrodes of pixel arrays to produce display frames are also well known and may be used in conjunction with the present invention.

FIGS. 4 and 5 illustrate one possible actuation protocol for creating a display frame on the 3×3 array ofFIG. 2.FIG. 4 illustrates a possible set of column and row voltage levels that may be used for pixels exhibiting the hysteresis curves ofFIG. 3. In theFIG. 4 embodiment, actuating a pixel involves setting the appropriate column to −V_bias, and the appropriate row to +ΔV, which may correspond to −5 volts and +5 volts respectively Relaxing the pixel is accomplished by setting the appropriate column to +V_bias, and the appropriate row to the same +ΔV, producing a zero volt potential difference across the pixel. In those rows where the row voltage is held at zero volts, the pixels are stable in whatever state they were originally in, regardless of whether the column is at +V_bias, or −V_bias. As is also illustrated inFIG. 4, it will be appreciated that voltages of opposite polarity than those described above can be used, e.g., actuating a pixel can involve setting the appropriate column to +V_bias, and the appropriate row to −ΔV. In this embodiment, releasing the pixel is accomplished by setting the appropriate column to −V_bias, and the appropriate row to the same −ΔV, producing a zero volt potential difference across the pixel.

FIG. 5B is a timing diagram showing a series of row and column signals applied to the 3×3 array ofFIG. 2 which will result in the display arrangement illustrated inFIG. 5A, where actuated pixels are non-reflective. Prior to writing the frame illustrated inFIG. 5A, the pixels can be in any state, and in this example, all the rows are at 0 volts, and all the columns are at +5 volts. With these applied voltages, all pixels are stable in their existing actuated or relaxed states.

In theFIG. 5A frame, pixels (1,1), (1,2), (2,2), (3,2) and (3,3) are actuated. To accomplish this, during a “line time” forrow1,columns1 and2 are set to −5 volts, andcolumn3 is set to +5 volts. This does not change the state of any pixels, because all the pixels remain in the 3-7 volt stability window.Row1 is then strobed with a pulse that goes from 0, up to 5 volts, and back to zero. This actuates the (1,1) and (1,2) pixels and relaxes the (1,3) pixel. No other pixels in the array are affected. To setrow2 as desired,column2 is set to −5 volts, andcolumns1 and3 are set to +5 volts. The same strobe applied to row2 will then actuate pixel (2,2) and relax pixels (2,1) and (2,3). Again, no other pixels of the array are affected.Row3 is similarly set by settingcolumns2 and3 to −5 volts, andcolumn1 to +5 volts. Therow3 strobe sets therow3 pixels as shown inFIG. 5A. After writing the frame, the row potentials are zero, and the column potentials can remain at either +5 or −5 volts, and the display is then stable in the arrangement ofFIG. 5A. It will be appreciated that the same procedure can be employed for arrays of dozens or hundreds of rows and columns. It will also be appreciated that the timing, sequence, and levels of voltages used to perform row and column actuation can be varied widely within the general principles outlined above, and the above example is exemplary only, and any actuation voltage method can be used with the systems and methods described herein.

FIGS. 6A and 6B are system block diagrams illustrating an embodiment of adisplay device40. Thedisplay device40 can be, for example, a cellular or mobile telephone. However, the same components ofdisplay device40 or slight variations thereof are also illustrative of various types of display devices such as televisions and portable media players.

Thedisplay device40 includes ahousing41, adisplay30, anantenna43, aspeaker45, aninput device48, and amicrophone46. Thehousing41 is generally formed from any of a variety of manufacturing processes as are well known to those of skill in the art, including injection molding, and vacuum forming. In addition, thehousing41 may be made from any of a variety of materials, including but not limited to plastic, metal, glass, rubber, and ceramic, or a combination thereof. In one embodiment thehousing41 includes removable portions (not shown) that may be interchanged with other removable portions of different color, or containing different logos, pictures, or symbols.

Thedisplay30 ofexemplary display device40 may be any of a variety of displays, including a bi-stable display, as described herein. In other embodiments, thedisplay30 includes a flat-panel display, such as plasma, EL, OLED, STN LCD, or TFT LCD as described above, or a non-flat-panel display, such as a CRT or other tube device, as is well known to those of skill in the art. However, for purposes of describing the present embodiment, thedisplay30 includes an interferometric modulator display, as described herein.

The components of one embodiment ofexemplary display device40 are schematically illustrated inFIG. 6B. The illustratedexemplary display device40 includes ahousing41 and can include additional components at least partially enclosed therein. For example, in one embodiment, theexemplary display device40 includes anetwork interface27 that includes anantenna43 which is coupled to atransceiver47. Thetransceiver47 is connected to theprocessor21, which is connected toconditioning hardware52. Theconditioning hardware52 may be configured to condition a signal (e.g. filter a signal). Theconditioning hardware52 is connected to aspeaker45 and amicrophone46. Theprocessor21 is also connected to aninput device48 and adriver controller29. Thedriver controller29 is coupled to aframe buffer28 and to thearray driver22, which in turn is coupled to adisplay array30. Apower supply50 provides power to all components as required by the particularexemplary display device40 design.

Thenetwork interface27 includes theantenna43 and thetransceiver47 so that theexemplary display device40 can communicate with one ore more devices over a network. In one embodiment thenetwork interface27 may also have some processing capabilities to relieve requirements of theprocessor21. Theantenna43 is any antenna known to those of skill in the art for transmitting and receiving signals. In one embodiment, the antenna transmits and receives RF signals according to the IEEE 802.12 standard, including IEEE 802.12(a), (b), or (g). In another embodiment, the antenna transmits and receives RF signals according to the BLUETOOTH standard. In the case of a cellular telephone, the antenna is designed to receive CDMA, GSM, AMPS or other known signals that are used to communicate within a wireless cell phone network. Thetransceiver47 pre-processes the signals received from theantenna43 so that they may be received by and further manipulated by theprocessor21. Thetransceiver47 also processes signals received from theprocessor21 so that they may be transmitted from theexemplary display device40 via theantenna43.

In an alternative embodiment, thetransceiver47 can be replaced by a receiver. In yet another alternative embodiment,network interface27 can be replaced by an image source, which can store or generate image data to be sent to theprocessor21. For example, the image source can be a digital video disc (DVD) or a hard-disc drive that contains image data, or a software module that generates image data.

Processor21 generally controls the overall operation of theexemplary display device40. Theprocessor21 receives data, such as compressed image data from thenetwork interface27 or an image source, and processes the data into raw image data or into a format that is readily processed into raw image data. Theprocessor21 then sends the processed data to thedriver controller29 or to framebuffer28 for storage. Raw data typically refers to the information that identifies the image characteristics at each location within an image. For example, such image characteristics can include color, saturation, and gray-scale level.

In one embodiment, theprocessor21 includes a microcontroller, CPU, or logic unit to control operation of theexemplary display device40.Conditioning hardware52 generally includes amplifiers and filters for transmitting signals to thespeaker45, and for receiving signals from themicrophone46.Conditioning hardware52 may be discrete components within theexemplary display device40, or may be incorporated within theprocessor21 or other components.

Thedriver controller29 takes the raw image data generated by theprocessor21 either directly from theprocessor21 or from theframe buffer28 and reformats the raw image data appropriately for high speed transmission to thearray driver22. Specifically, thedriver controller29 reformats the raw image data into a data flow having a raster-like format, such that it has a time order suitable for scanning across thedisplay array30. Then thedriver controller29 sends the formatted information to thearray driver22. Although adriver controller29, such as a LCD controller, is often associated with thesystem processor21 as a stand-alone Integrated Circuit (IC), such controllers may be implemented in many ways. They may be embedded in theprocessor21 as hardware, embedded in theprocessor21 as software, or fully integrated in hardware with thearray driver22.

Typically, thearray driver22 receives the formatted information from thedriver controller29 and reformats the video data into a parallel set of waveforms that are applied many times per second to the hundreds and sometimes thousands of leads coming from the display's x-y matrix of pixels.

In one embodiment, thedriver controller29,array driver22, anddisplay array30 are appropriate for any of the types of displays described herein. For example, in one embodiment,driver controller29 is a conventional display controller or a bi-stable display controller (e.g., an interferometric modulator controller). In another embodiment,array driver22 is a conventional driver or a bi-stable display driver (e.g., an interferometric modulator display). In one embodiment, adriver controller29 is integrated with thearray driver22. Such an embodiment is common in highly integrated systems such as cellular phones, watches, and other small area displays. In yet another embodiment,display array30 is a typical display array or a bi-stable display array (e.g., a display including an array of interferometric modulators).

Theinput device48 allows a user to control the operation of theexemplary display device40. In one embodiment,input device48 includes a keypad, such as a QWERTY keyboard or a telephone keypad, a button, a switch, a touch-sensitive screen, a pressure- or heat-sensitive membrane. In one embodiment, themicrophone46 is an input device for theexemplary display device40. When themicrophone46 is used to input data to the device, voice commands may be provided by a user for controlling operations of theexemplary display device40.

Power supply50 can include a variety of energy storage devices as are well known in the art. For example, in one embodiment,power supply50 is a rechargeable battery, such as a nickel-cadmium battery or a lithium ion battery. In another embodiment,power supply50 is a renewable energy source, a capacitor, or a solar cell, including a plastic solar cell, and solar-cell paint. In another embodiment,power supply50 is configured to receive power from a wall outlet.

In some implementations control programmability resides, as described above, in a driver controller which can be located in several places in the electronic display system. In some cases control programmability resides in thearray driver22. Those of skill in the art will recognize that the above-described optimization may be implemented in any number of hardware and/or software components and in various configurations.

The details of the structure of interferometric modulators that operate in accordance with the principles set forth above may vary widely. For example,FIGS. 7A-7E illustrate five different embodiments of the movablereflective layer14 and its supporting structures.FIG. 7A is a cross section of the embodiment ofFIG. 1, where a strip ofmetal material14 is deposited on orthogonally extending supports18. InFIG. 7B, the moveablereflective layer14 is attached to supports at the corners only, ontethers32. InFIG. 7C, the moveablereflective layer14 is suspended from adeformable layer34, which may comprise a flexible metal. Thedeformable layer34 connects, directly or indirectly, to thesubstrate20 around the perimeter of thedeformable layer34. These connections are herein referred to as support posts. The embodiment illustrated inFIG. 7D has support post plugs42 upon which thedeformable layer34 rests. The movablereflective layer14 remains suspended over the cavity, as inFIGS. 7A-7C, but thedeformable layer34 does not form the support posts by filling holes between thedeformable layer34 and theoptical stack16. Rather, the support posts are formed of a planarization material, which is used to form support post plugs42. The embodiment illustrated inFIG. 7E is based on the embodiment shown inFIG. 7D, but may also be adapted to work with any of the embodiments illustrated inFIGS. 7A-7C as well as additional embodiments not shown. In the embodiment shown inFIG. 7E, an extra layer of metal or other conductive material has been used to form abus structure44. This allows signal routing along the back of the interferometric modulators, eliminating a number of electrodes that may otherwise have had to be formed on thesubstrate20.

In embodiments such as those shown inFIG. 7, the interferometric modulators function as direct-view devices, in which images are viewed from the front side of thetransparent substrate20, the side opposite to that upon which the modulator is arranged. In these embodiments, thereflective layer14 optically shields some portions of the interferometric modulator on the side of the reflective layer opposite thesubstrate20, including thedeformable layer34 and thebus structure44. This allows the shielded areas to be configured and operated upon without negatively affecting the image quality. This separable modulator architecture allows the structural design and materials used for the electromechanical aspects and the optical aspects of the modulator to be selected and to function independently of each other. Moreover, the embodiments shown inFIGS. 7C-7E have additional benefits deriving from the decoupling of the optical properties of thereflective layer14 from its mechanical properties, which are carried out by thedeformable layer34. This allows the structural design and materials used for thereflective layer14 to be optimized with respect to the optical properties, and the structural design and materials used for thedeformable layer34 to be optimized with respect to desired mechanical properties.

FIG. 8 is a cross section of an example of display system that comprises an example of the array oflight modulators30 illuminated by anilluminator110 comprising an array of illuminating orlight turning elements112. As illustrated in the example system ofFIG. 8, thelight turning elements112direct light124 such as from alight source122 to thelight modulators126 and then to aviewing position128. In one embodiment, thelight modulators126 comprise reflective light modulators such as the interferometric modulators such as illustrated inFIGS. 1,7A,7B,7C,7D, and7E. Other embodiments may comprise other types of light modulators. In one embodiment, thelight turning elements112 comprise at least partially reflective surfaces configured to direct the light124 to thelight modulators126. In other embodiments, theilluminator110 may comprise various structures configured to illuminate thelight modulators126. For example, thelight turning elements112 may comprise any other suitable structure for directing a pattern of light onto thelight modulators126. Moreover, thelight turning elements112 may comprise materials, e.g., photoluminescent or electroluminescent materials, configured to direct a pattern of illumination onto thelight modulators126.

FIG. 9 is a cross section of an example of display system such as illustrated inFIG. 8 that comprises anarray30 oflight modulators126 illuminated by an array of reflectivelight turning elements112. The examplelight turning elements112 inFIG. 9 each comprise surfaces130 and132 that are configured to direct light to thelight modulators126. In the illustrated embodiment, the light124 enters through a side surface of theilluminator110. Theilluminator110 internally reflects the light124 until the light124 strikes thesurfaces130 and132 so as to be directed onto one or more of thelight modulators126, which in turn modulate the light124 and direct a portion of the modulated light to theviewing position128. In one embodiment, theilluminator110 is configured with respect to the light source (e.g.,light source122 ofFIG. 8) so that total internal reflectance of the light124 within theilluminator110 reduces loss of the light124 except when reflected by thelight turning elements112 towards thelight modulators126.

FIG. 10A is a cross section of an example of an array of periodically spacedlight turning elements112 in theilluminator110 such as illustrated inFIG. 9. InFIG. 10, eachlight turning element112 is represented schematically and separated from adjacentlight turning elements112 by a substantially fixed distance P_FLthat is indicative of the periodicity of thelight turning elements112 in theilluminator110. Note that in some embodiments, the distance P_FLis gradually decreased as the distance within theilluminator110 increases from a light source. However, for a particular line of light turning elements P_FL, the distance P_FLbetween each adjacent line oflight turning elements112 in such an embodiment is substantially the same. Thus, a Moiré pattern may still be visible.

FIG. 10B is a perspective view of an example of theilluminator110 comprising the array of periodically spaced reflectivelight turning elements112 such as illustrated inFIG. 10A. In the embodiment illustrated inFIG. 10B, thesurfaces130 and132 form lines, e.g., rows or columns, approximately along one axis of theilluminator110. Thus, eachlight turning element112 may illuminate a plurality oflight modulators126, for example, one or more rows or columns oflight modulators126. The periodicity, P_FL, of the array oflight turning elements112 is illustrated with reference to thereflective surfaces130 and132 of each of thelight turning elements112.FIG. 10C is a top view further illustrating the example of theilluminator110 comprising the periodic array of periodically spaced reflectivelight turning elements112 such as illustrated inFIG. 10B.

FIG. 11A illustrates a schematic cross section view of a periodically arrangedlight turning elements112 and a light modulator array such as illustrated inFIG. 10A. Each of thelight turning elements112 is separated by a distance P_FLindicative of the periodicity of the array oflight turning elements112.FIG. 11A illustrates light124 periodically directed by thelight turning elements112 onto themodulator array30.

FIG. 11B illustrates a cross section view of the example of the periodically arranged reflectivelight turning array110 such as illustrated inFIG. 11A. Thelight reflecting surfaces130 and132 of each of the illustratedlight turning elements112 are positioned at an angle of θ_FL.

It has been found that when a periodic array oflight turning elements112 is positioned between a periodic array oflight modulators126 andviewing positions128 of thelight modulators126, the superposition of the two periodic structures tends to create visual artifacts. These visual artifacts typically comprise lines or two dimensional patterns of lights formed as an interference or Moiré pattern.

FIG. 12 is a top view exemplifying Moiré patterns formed by three sets of two superimposed periodic arrangements of lines. In particular,FIG. 12 illustrates Moiré patterns formed inregions212,214, and216 where apattern202 of lines and apattern208 of lines overlap at angles of 10°, 20°, and 30°, respectively. As illustrated in each of theoverlap regions212,214, and216, an interference pattern of somewhat horizontal lines (angled slightly toward the lower right corner ofFIG. 12). It is to be recognized that while the Moiré patterns ofFIG. 12 are formed by patterns of lines that overlap at different angles, it is the resulting difference in superimposed periodicity that generates the artifacts of the Moiré pattern. Thus, such artifacts can be generated by two overlapping periodic patterns such as theilluminator110 and thelight modulator array30 regardless of the alignment of the two arrays. It has been found that by arranging thelight turning elements112 of theilluminator110 to direct a nonuniformly varying pattern of light to thelight modulators126, the Moiré patterns are substantially reduced. Note that a periodic arrangement oflight turning elements112 such as inFIG. 11A generally produces a nonuniform pattern of light. However, such a pattern of light on thelight modulators126 varies substantially uniformly in accordance with the pattern oflight turning elements112. As discussed in further detail below with respect to various embodiments, a nonuniform arrangement oflight turning elements112 directs a nonuniformly varying pattern of light on thelight modulators126 that varies nonuniformly according to the nonuniform arrangement of thelight turning elements112.

FIG. 13A illustrates a schematic cross section view of an example of anlight turning array110 in which thelight turning elements112 are aperiodically or nonuniformly spaced. Each oflight turning elements112 is positioned from adjacentlight turning elements112 by different distances, e.g., P_i, P_i+1, P_i+2, etc. Thus,light rays124 reflected by thelight turning elements112 collectively define a non-periodically, or nonuniformly varying, pattern of light illuminating thelight modulators126.

FIG. 13B illustrates a cross section view of the nonuniformly arranged reflectivelight turning array110 such as illustrated schematically inFIG. 13A. In the embodiment illustrated inFIG. 13B, thesurface130 eachlight turning element112 is positioned at substantially the same angle θ_FLrelative to thesurface132 of the samelight turning element112. In contrast, the position of each adjacent line oflight turning elements112 varies, e.g., the distances P_i, P_i+1, P_i+2, vary. For example, in one embodiment, each value P_iwithin the array is different. In another embodiment, the distances repeat at a sufficiently low frequency within thelight turning array110 that the interaction with thelight modulator array30 produces no substantial visible artifacts.

FIG. 14 illustrates a top view of the nonuniformly arrangedlight turning array110 illustrated inFIG. 13B.FIG. 14 illustrates the positions X′_i, X′_i+1, X′_i+2, etc. of each of the light turning elements112 (e.g., the position of the intersection of thesurface130 and the surface132). Each of these positions X′_i, X′_i+1, X′_i+2is offset from a corresponding periodically spaced position X_i, X_i+1, X_i+2by an offsetdistance140a,140b,140c,140d,140e(collectively offset distances140). Each of the offset distances140 may be different in aparticular array110. Alternatively, each of the offset distances140 in aparticular array110 may be selected randomly, e.g., from within a range of available offsets. Note that as used herein random refers to random and pseudo random selections. In yet another embodiment, each offsetdistance140a,140b,140c,140d,140emay be selected to have a pattern that repeats throughout thearray110 with a frequency that is too low to result in any substantial visible artifacts. The offset distances140 may be selected, randomly or otherwise, to be distributed according to a particular distribution within a range of distances, for example, the distances may be distributed with uniform or Gaussian distribution. In one embodiment, each offset distance (X′_i-X_i) is determined by multiplying a random number between −1 and +1 with the separation from the first neighboring unit, such as (X_i+1-X_i) or (X_i-X_i−1). In another embodiment, the random number multiplier is between −0.5 and 0.5. In yet another embodiment, at least two offset distances are selected and applied in a random order to each light turning element X_i(this order can be completely random, or a prescribed random sequence such as the Fibonacci, Thue-Morse, or other similar random numerical sequences. In one embodiment, the at least two offset distances are selected randomly so that at least one of them is larger than 10% of the average separation between light turning elements. It is to be recognized that randomness selection in the arrangement oflight turning elements112 is generally incorporated at the design or manufacturing stage. During manufacturing, a particular arrangement oflight turning elements112 may be substantially reproduced once or many times.

FIG. 15A illustrates a top view of another embodiment of another example of an illuminator comprising an array of a nonuniformly arrangedlight turning elements112 that is conceptually similar to that ofFIG. 13A. In the example illustrated inFIG. 15A, thelight turning elements112 comprise regions of theilluminator110 that include the reflectingsurfaces130 and132. Thelight turning elements112 ofFIG. 15A may be varied in both size and position so that theilluminator110 directs a nonuniformly varying pattern of light to the modulator array30 (not shown) in one or both of vertical and horizontal dimensions. In the embodiment illustrated inFIG. 15A, a line of thelight turning elements112 is distributed generally along lines X_j, X_j+1, . . . X_k.. In the illustrated embodiment, each of thelight turning elements112 is offset by a random distance in both the vertical (Y) and horizontal (X) from a position along one of the lines X_j, . . . X_k.. The vertical and horizontal offsets may be determined in any suitable way, including those discussed with reference toFIG. 14. In one embodiment, the vertical offsets may be zero.

FIG. 15B illustrates a top view of aportion150 of theilluminator110 ofFIG. 15A in more detail. The example of theportion150 compriseslight turning elements112a,112b, and112cthat are each offset in the horizontal direction along an axis X_k, where k is a value between 1 and N, the number of lines in a particular illuminator, and where k represents a particular vertical line of light turning elements in theilluminator110. In one embodiment, offset of thereflective surfaces130 and132 of eachlight turning element112a,112b, or112cvaries by horizontal offsets that change at positions Y_k,j, where j is a value between 1 and M, the number oflight turning elements112 in a particular line in a particular illuminator, and where j represents a particular vertical position of a particularlight turning element112 in the line k oflight turning elements112. The vertical length of the lightturning element elements112, e.g.,element112bis determined by a corresponding vertical position, Y_k,jand the vertical position Y_k,j+1of theadjacent element112c. Each vertical position Y_k,jmay be selected so that eachlight turning element112 has a vertical size or extent within a particular range, e.g., ΔY_minand ΔY_max. In one embodiment, the vertical size of eachlight turning element112 is randomly distributed within the range e.g., ΔY_minand ΔY_max. Thelight turning element112bat vertical position Y_k,jis also offset by an amount ΔX_k,jfrom the line X_k. In one embodiment, the vertical positions Y_k,jare distributed within a particular or predetermined range of distances, e.g., between ΔX_minand ΔX_max. In one embodiment, the positions Y_k,jare randomly distributed within the range of distances. It is to be recognized that while in one embodiment, eachlight turning element112 is desirably offset in both vertical and horizontal directions, in other embodiments, thelight turning element112 may be offset only in one of the vertical or horizontal directions. Theilluminator110 ofFIGS. 15A and 15B thus is configured to direct a nonuniformly varying pattern of light to light modulators such as thearray30 oflight modulators126 ofFIG. 11A.

FIG. 16A is a graphical illustration of a uniform distribution illustrative of the nonuniform distribution oflight turning elements112 in one embodiment of theilluminator110. As noted above, in one embodiment, the horizontal offset positions X_k,jof thelight turning elements112 along a line of light turning elements are randomly distributed within a range of distances, e.g., ΔX_minand ΔX_max. In one embodiment, the offset for eachlight turning element112 may be selected according to a uniform distribution such as illustrated inFIG. 16A. Hence, the distribution of offsets is a uniform distribution that results in a nonuniform arrangement of the light turning elements.

FIG. 16B is a graphical illustration of a normal distribution illustrative of the nonuniform distribution oflight turning elements112 in one embodiment of theilluminator110. In one embodiment, the offset for eachlight turning element112 may be selected according to a normal (Gaussian) distribution such as illustrated inFIG. 16A. It is to be recognized that in various embodiments thelight turning elements112 may be distributed based on any suitable mathematical distribution that generates a substantially nonuniform array.

FIG. 17A illustrates a top view of another example of theilluminator110 comprising an array of a nonuniformly arrangedlight turning elements112 that is conceptually similar to that ofFIG. 13A. In the embodiment illustrated inFIG. 17A, a nonuniformly varying pattern of reflected light is achieved by rotating each of thelight reflecting elements112 about apoint170 by an angle a_k. Eachlight turning element112 may have a different angle a_kof rotation (e.g., from vertical line X_k) that is distributed within a range a_minto a_max. In one embodiment, the angles a_kare randomly distributed within the range, e.g., according to a uniform or Gaussian distribution. The angles may be selected in any suitable way, including according to methods similar to those discussed with reference toFIG. 14.

FIG. 17B illustrates a top view of another example of theilluminator110 comprising an array of a nonuniformly arrangedlight turning elements112 that is conceptually similar to that ofFIG. 17A. In the example ofFIG. 17A, each of thelight turning elements112 is rotated about thepositions170 along each line X_k, which are with substantially equal distances P_FLhorizontally between each line X_kon theilluminator110. In the example ofFIG. 17B, eachlight turning element112 is rotated about a point that is randomly selected at a distance X′_kalong the line X_k. The distance X′_kof each line X_kmay be selected from a range of distances, e.g., ΔX′_minand ΔX′_max. In one embodiment, the distances X′_kare randomly distributed within the range, e.g., according to a uniform or Gaussian distribution. Thus, the periodicity of the pattern of light directed from thelight turning elements112 ofFIG. 17B to the light modulators30 (not shown) is further reduced with respect to the embodiment illustrated inFIG. 17A. In other embodiments, the offset distances X′_kmay be selected from a set in which each distance in the set is used one or more times. In one such an embodiment, any repetition of particular offset distances X′_kis minimized and preferably offset distances X′_kof adjacentlight turning elements112 are different. The distances X′_kmay be determined in any suitable way, including those discussed with reference toFIG. 14.

FIG. 18A illustrates a top view of another example of theilluminator110 comprising an array of a nonuniformly arrangedlight turning elements112 that is conceptually similar to that ofFIG. 13A. In the example ofFIG. 18A, each of thelight turning elements112 is positioned along each line X_k. To direct a nonuniformly varying pattern of light, the reflectingsurface130 of eachlight turning element112, e.g.,element112a, intersects the reflectingsurface132 at an angle, e.g., θ_k. In one embodiment, the angle θ_k, θ_k+1, θ_k+2, corresponding to each of, at least, adjacentlight turning elements112 is different. For example, eachlight turning element112 may have a different angle θ_kthat is distributed within a range θ_minto θ_max. In one embodiment, the angle θ_kare randomly distributed within the range, e.g., according to a uniform or Gaussian distribution. In other embodiments, the angles θ_kmay be selected from a set in which each angle in the set is used one or more times. In one such an embodiment, any repetition of particular angles θ_kis minimized and preferably angles of adjacentlight turning elements112 are different. The angles θ_kmay be selected in any suitable way, including according to methods similar to those discussed with reference toFIG. 14. In one embodiment, the range θ_minto θ_maxis selected to exceed the larger of the vertical angular divergence of the light emitted by the illuminator in the plane of the θ_krotation and of +/−1°, which is the angular cone typically collected by the human eye.

FIG. 18B illustrates a schematic cross section view of the nonuniformly arrangedilluminator110 ofFIG. 18A in relation to thearray30 oflight modulators130. As illustrated schematically, each oflight turning elements112 direct light from theilluminator110 at different angles to generate a nonuniformly varying pattern of light124 that is modulated, and in the illustrated example reflected, by thearray30 oflight modulators126. In particular, the distances P_i, P_i+1between thelight rays124 directed onto thearray30 vary nonuniformly within theilluminator110.

In one embodiment, theilluminator110 is formed separately from thelight modulator array30 and then applied to thearray30. In another embodiment, theilluminator110 is formed on or above thesubstrate20.

It is to be recognized that while certain embodiments are disclosed with reference to horizontal or vertical axis, in other embodiments, the arrangement of components of theilluminator110 orlight modulator array30 with respect to horizontal and vertical axis may be reversed. Furthermore, it is to be recognized that embodiments may include combinations of features described with respect to the disclosed examples oflight turning elements112 that direct nonuniformly varying patterns of light to thelight modulator array130, regardless of whether such combinations are expressly disclosed herein.

While the above detailed description has shown, described, and pointed out novel features of the invention as applied to various embodiments, it will be understood that various omissions, substitutions, and changes in the form and details of the device or process illustrated may be made by those skilled in the art without departing from the spirit of the invention. As will be recognized, the present invention may be embodied within a form that does not provide all of the features and benefits set forth herein, as some features may be used or practiced separately from others. The scope of the invention is indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.

Claims (34)

1. A display device, comprising:

a plurality of light modulators disposed on a substrate; and

a plurality of illumination elements formed substantially along a plane and configured to extract light from a light guide, and to transform the extracted light into a non-uniformly varying pattern of light, the plurality of illumination elements being further configured to direct the non-uniformly varying pattern of light to the light modulators, wherein each of the illumination elements comprises at least one surface defining an angle with respect to the substrate and wherein each of said surfaces is configured to direct the non-uniformly varying pattern of light to at least one of said light modulators.

2. The device ofclaim 1, further comprising a light source configured to provide light to the plurality of illumination elements.

3. The device ofclaim 1, wherein the surfaces of at least two of the illumination elements define different angles with respect to the substrate.

4. The device ofclaim 1, wherein the illumination elements are arranged in a non-uniform pattern.

5. The device ofclaim 4, wherein each of the illumination elements is positioned adjacent to at least one other of the illumination elements and each of the illumination elements is positioned at a non-uniform offset from said at least one other of the illumination elements.

6. The device ofclaim 5, wherein said offset comprises an offset in two dimensions.

7. The device ofclaim 5, wherein at least two of the illumination elements have different sizes.

8. The device ofclaim 4, wherein the illumination elements are arranged in a plurality of lines and wherein the lines are non-parallel to each other.

9. The device ofclaim 8, wherein each of the lines has a midpoint, and wherein the midpoints of the lines are arranged non-uniformly within the plurality of illumination elements.

10. The device ofclaim 1, wherein light modulators comprise interferometric light modulators.

11. The device ofclaim 1, further comprising:

a processor that is in electrical communication with said light modulators, said processor being configured to process image data;

a memory device in electrical communication with said processor.

12. The device ofclaim 11, further comprising a driver circuit configured to send at least one signal to said light modulators.

13. The device ofclaim 12, further comprising a controller configured to send at least a portion of said image data to said driver circuit.

14. The device ofclaim 11, further comprising an image source module configured to send said image data to said processor.

15. The device ofclaim 14, wherein said image source module comprises at least one of a receiver, transceiver, and transmitter.

16. The device ofclaim 11, further comprising an input device configured to receive input data and to communicate said input data to said processor.

17. A display device comprising:

a plurality of light modulators; and

a plurality of illumination elements arranged in a plurality of lines, each line of the plurality of lines being disposed at a non-uniform offset from each adjacent line of the plurality of lines, the illumination elements configured to direct light to the light modulators.

18. A display device comprising:

a plurality of light modulators; and

a plurality of discontinuous illumination elements arranged along a series of lines and configured to direct light to the light modulators, wherein each of the plurality of discontinuous illumination elements is arranged along, and offset from, one of the series of lines and wherein the series of lines is formed substantially in a plane.

19. A display device comprising:

a plurality of interferometric modulators disposed on a substrate and configured for modulating light; and

a plurality of illumination elements configured for extracting light from a light guide, for transforming the extracted light into a non-uniformly varying pattern of light and for illuminating the interferometric modulators with the non-uniformly varying pattern of light.

20. The device ofclaim 19, wherein the plurality of illumination elements comprises means for reflecting light.

21. The device ofclaim 19, wherein each of the illumination elements comprises a surface defining an angle with respect to the substrate, wherein each of said surfaces is configured to direct light to said interferometric modulators.

22. A method of making an illuminator, the method comprising:

forming a plurality of illumination elements substantially along a plane, the illumination elements configured to extract light from a light guide, to transform the extracted light into a non-uniformly varying pattern of light and to direct the non-uniformly varying pattern of light to an array of light modulators.

23. The device ofclaim 22, further comprising forming the array of light modulators on a substrate.

24. The device ofclaim 23, wherein forming the plurality of illumination elements comprises forming the plurality illumination elements above the substrate.

25. The device ofclaim 22, wherein forming each of the plurality of illumination elements comprises forming at least one surface configured to direct the non-uniformly varying pattern of light onto at least one light modulator in the array of light modulators.

26. The device ofclaim 25, wherein the surfaces of at least two of the illumination elements define different angles with respect to a substrate on which the light modulators are formed.

27. The device ofclaim 22, wherein the illumination elements are arranged in a non-uniform pattern.

28. The device ofclaim 27, wherein each of the illumination elements is formed at a position adjacent to at least one other of the illumination elements and each of the illumination elements is formed at a position at a non-uniform offset from said at least one other of the illumination elements.

29. The device ofclaim 27, wherein the illumination elements are arranged in a plurality of lines and wherein the lines are non-parallel to each other.

30. The device ofclaim 29, wherein each of the lines has a midpoint, and wherein the midpoints of the lines are arranged non-uniformly within the plurality of illumination elements.

31. The device ofclaim 22, wherein the light modulators comprise interferometric light modulators.

32. A method, comprising:

illuminating a plurality of illumination elements with light;

directing a non-uniformly varying pattern of the light formed from the illumination elements to a plurality of interferometric light modulators; and

interferometrically modulating the non-uniformly varying pattern of light with the interferometric light modulators.

33. The method ofclaim 32, further comprising disposing the plurality of light modulators on a substrate, wherein each of the illumination elements comprises at least one surface defining an angle with respect to the substrate and wherein each of said surfaces is configured to direct the non-uniformly varying pattern of light to at least one of said light modulators.

34. The method ofclaim 32, wherein the illumination elements are arranged in a non-uniform pattern.

Images